I like how the article points this out.
On top of them having chosen an old section, they also chose a geological soft spot that was easier to dig through. You can say the wall is ineffective but they had to choose a specific location that was poorly patrolled in order to have even any success of entry. It deterred people, until they chose to dig.The record-large group that entered the U.S. on Monday, meanwhile, made the crossing in a particularly rural area, a 26-mile stretch of an older section of barrier that Border Patrol said was being monitored by only three agents.
Can you tell me why they dug? Is it because it was far more quiet than, say, cutting through metal with a grinder or saw? It's almost like the wall deterred these people from taking an action that would have got them caught. How strange is that.